Synchronized multiple-radio antenna systems and meihods

ABSTRACT

Multi-radio antenna apparatuses and stations for wireless networks including multiple radios coupled to a single transmit/receive antenna, in which the antenna is highly synchronized by an external (e.g., GPS) signal. These multi-radio antenna systems may provide highly resilient links. Synchronization may allow these apparatuses to organically scale the transmission throughput while preventing data loss. The single transmit/receive antenna may have a single dish or a compound (e.g., a single pair of separate transmitting and receiving dishes) and connections for two or more radios.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 16/452,332, titled “SYNCHRONIZED MULTIPLE-RADIO ANTENNA SYSTEMSAND METHODS,” filed on Jun. 25, 2019, which is a continuation of U.S.patent application Ser. No. 16/140,389, titled “SYNCHRONIZEDMULTIPLE-RADIO ANTENNA SYSTEMS AND METHODS,” filed on Sep. 24, 2018, nowU.S. Pat. No. 10,381,739, which is a continuation of U.S. patentapplication Ser. No. 15/702,658, titled “SNYCHRONIZED MULTIPLE-RADIOANTENNA SYSTEMS AND METHODS,” filed on Sep. 12, 2017, now U.S. Pat. No.10,084,238, which is a continuation of U.S. patent application Ser. No.15/289,487, titled “SNYCHRONIZED MULTIPLE-RADIO ANTENNA SYSTEMS ANDMETHODS,” filed on Oct. 10, 2016, now U.S. Pat. No. 9,761,954, whichclaims priority to U.S. Provisional Patent Application Nos. 62/239,831,titled “SYNCHRONIZED MULTIPLE-RADIO ANTENNA SYSTEMS AND METHODS”, filedon Oct. 9, 2015, and U.S. Provisional Patent Applications No.62/277,862, titled “SYNCHRONIZED MULTIPLE-RADIO ANTENNA SYSTEMS ANDMETHODS” filed on Jan. 12, 2016, each of which is herein incorporated byreference in its entirety.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference in their entirety to the sameextent as if each individual publication or patent application wasspecifically and individually indicated to be incorporated by reference.

FIELD

The apparatuses described herein generally relate to antenna havingmultiple radios connected to a single emitter/receiver for simultaneoustransmission from each of the radios. The radios may be balanced (e.g.,data packet load balanced).

BACKGROUND

Wireless networks are typically realized using point-to-multipointradios. Also, some Internet service providers (ISPs) provide Internetconnectivity to remote locations by installing radio towers that usepoint-to-point antennas to relay the network connection to the remotelocation. Some radio towers include both point-to-point andpoint-to-multipoint radios that are driven by a ground-level basestation at the base of the tower.

Space in radio towers is often at a premium, and may be expensive. Ingeneral antenna assemblies, including point-to-point andpoint-to-multipoint antennas assemblies typically include a single radiothat operate over the full bandwidth, and transmit and receive all RFdata through the antenna. Each antenna requires space and separationfrom other antenna to prevent undesirable interference, requiring asignificant amount of tower space and therefore expense. Althoughantenna systems in which more than one radio may be used, these systemstypically require a great deal of coordination and communication betweeneach radio of the system, resulting a slowing and inefficiencies of theresulting antenna system and also increased cost. Further, such systemsare not well able to adapt to changes in the transmission rate (ordisruption of) one or more of the radios. What is needed are antennasystems that may use multiple radios connected to the same antennaassembly in a scalable (e.g., linearly scalable) manner withoutrequiring direct communication between the multiple radios.

In any multiple-radio apparatus it may be useful to split/combine RFsignals transmitted. Combiner-splitters for RF systems are known. Forexample, the Wilkinson divider splitter/Wilkinson combiner is a form ofpower splitter/power combiner that is used in microwave applications anduses quarter wave transformers, which may be fabricated as quarter wavelines on printed circuit boards. These apparatuses may provide a cheapand simple splitter/divider/combiner. The Wilkinson splitter/combinermay be formed entirely of printed circuit board transmission linecomponents, or it may include other forms of transmission lines (e.g.coaxial cable) or lumped circuit elements (inductors and capacitors).

A Wilkinson power divider is a passive electronic device that splits asingle RF input signal into two (n=2) or more (n≥3) in-phase output RFsignals. Such devices can also be used in the opposite direction tocombine multiple in-phase RF signals into a single RF output. Thedetails of design and operation for these devices are well known. Suchdevices are typically realized using resistors and impedance-transformersections of RF transmission line (such as coaxial line, microstrip,stripline, etc.) in various configurations.

Thus, a Wilkinson power divider or Wilkinson splitter may be used as amultiple port device, including as a two way divider. Wilkinsonsplitter/combiners have known benefits and problems. Advantages include:Simplicity, low cost, relatively low loss, and reasonable isolation. Forexample a Wilkinson divider/splitter/combiner can be realized usingprinted components on a printed circuit board. It is also possible touse lumped inductor and capacitor elements, but this complicates theoverall design. Although the cost may otherwise be very low, to reducelosses, a low-loss PCB substrate may be used, which may increase thecost. Loss may arise from the division of the power between thedifferent ports, though components used for a Wilkinson splitter can berelatively low loss, especially when PCB transmission lines are usedalong with low-loss PCB substrate materials. Disadvantages oftraditional Wilkinson splitters may include a reduction in frequencyresponse. As the Wilkinson splitter is based around the use of quarterwave transmission lines, it has a limited bandwidth.

Described herein are apparatuses (systems and methods) that my addressthe issues raised above, and may take advantage of simple system ofsplitter/combiners (including chains of splitter/combiners) whileenhancing performance, e.g., throughput, of the overall antennaapparatus.

SUMMARY OF THE DISCLOSURE

The present invention relates to methods and apparatuses (includingdevices and systems) for combining a plurality of radio frequency (RF)radios so that all of the radios can simultaneously and synchronouslysend or synchronously receive RF signals from a single antenna.

Described herein are methods of combining a plurality of radios so thatthey simultaneously send or receive from a single antenna. These methodsmay include: passively combining the inputs of each of the plurality ofradios into a single output coupled to the single antenna; synchronizingeach of the plurality of radios using a master synchronization signal(e.g., global positioning satellite, or GPS, signal), so that each ofthe plurality of radios is operating on a same duty cycle;simultaneously transmitting RF signals from each of the plurality ofradios using the single antenna, wherein each of the plurality of radiostransmits in different frequency channels; and simultaneously receivingRF signals in each of the plurality of radios using the single antenna.

Any of these methods may also include synchronizing the remote (e.g.,slave) radios that communicate with the combined (master) radios). Theslave devices may themselves be combined, or they may be separateradios.

For example, a method of combining a plurality of radios so that theysimultaneously send or receive from a single antenna may include:passively combining the inputs of each of the plurality of radios into asingle output coupled to the single antenna; periodically synchronizingeach of the plurality of radios using a GPS signal, wherein each of theplurality of radios is operating on a same duty cycle; transmitting asynchronized master timing preamble from each of the plurality ofradios; simultaneously transmitting RF signals from each of theplurality of radios using the single antenna, wherein each of theplurality of radios operates in different frequency channels;simultaneously receiving RF signals in each of the plurality of radiosusing the single antenna; and synchronizing a duty cycle of a firstremote slave radio using the master timing preamble.

Any of the methods described herein may include attaching each of theplurality of radios to a single antenna. The radios may be attached viaa mount or other attachment that holds the radio in communication withthe multiplexer and the single antenna. Each antenna may be configuredto transmit/receive in multiple polarities (e.g., vertical/horizontal,etc.) and the input or inputs used to connect the radio to the passivecombiner/divider may account for this, e.g., including two or more ports(connectors).

In general, all of the radios (in the plurality of radios) connected tothe same antenna may had a synchronized duty cycle for Transmission (Tx)and receiving (Rx). For example, the duty cycle of the plurality ofradios is 50/50, 67/33, or 25/75 (any other duty cycle ratio may beused).

Each of the plurality of radios typically operates in a differentfrequency channel. The different frequency channels may be adjacent(e.g., immediately adjacent) to each other without a guard band betweenadjacent channels. For example, each channel may be a 20 MHz channel andthe GPS-synchronized radios may talk simultaneously over the single linkon directly adjacent channels, such as one at 5780 MHz and the other at5800 MHz.

Any of the apparatuses described herein may operate in MIMO,particularly when acting in the shared antenna mode described herein.

Any of the methods and apparatuses described herein may be configuredfor synchronization using an outside, global synchronization signalsource, such as an external GPS. Thus, none of the radios of theplurality of radios may (or must) communicate directly about thesynchronization. Thus, these methods including using an externalsynchronization signal such as a GPS signal comprises synchronizing eachof the plurality of radios without communication between the radios. Forexample, each of the plurality of radios may independently receive theGPS signal. The synchronization of each of the plurality of radios usinga GPS signal may occur about every 1 second, e.g., +/−15 nanoseconds. Ingeneral, the global synchronization signal does not necessarily have tobe GPS but may be some other form of sync amongst the master radios tokeep their TX-RX frames aligned.

In any of these methods the step of simultaneously transmitting RFsignals from each of the plurality of radios may comprise simultaneouslytransmitting a synchronized master timing preamble from each of theplurality of radios. A master timing preamble may be sent before eachtransmission and may include information about the signals beingtransmitted. The master timing preamble it typically synchronized (e.g.,by master timing tick, based on the GPS signal).

As mentioned, any of these methods may include synchronizing a dutycycle of a first remote slave radio using a synchronized master timingpreamble transmitted by each of the plurality of radios, and may furtherinclude synchronizing a duty cycle of a second remote slave radio with asynchronized mater timing preamble. Any of the slave radioscommunicating with the master devices may synchronize by sliding areceiver frame until the master timing preamble is identified. This ispossible even when the remote (slave) radio false synchronizes toanother timing preamble, such as a slave preamble symbol from a nearby(slave) radio.

Thus, any of these methods may include transmitting RF signals from thefirst remote slave radio to the single antenna during a transmissionframe determined by the synchronized duty cycle of the first remoteslave radio.

In general, passively combining the inputs of each of the plurality ofradios into the single output coupled to the single antenna may includepassing inputs from each of the plurality of radios through a Wilkinsonpower divider/combiner having an output coupled to the single antenna.

The apparatuses described herein may be configured to operate in anunsynchronized mode or in a synchronized mode. For example, any of thesemethods may also include switching from an unsynchronized mode ofoperation to a shared antenna mode in which each of the plurality ofradios is synchronized using the GPS signal to operate on the same dutycycle.

Also described herein are apparatuses that are configured to perform themethods described above. These apparatuses may include hardware,software and/or firmware for performing the functions described herein.For example, described herein are multiplexer apparatuses for combininga plurality of radios so that they simultaneously send or receive from asingle antenna. Such apparatuses may include: a first external mountconfigured to hold a first radio, and a first input configured toconnect to an input of the first radio; a second external mountconfigured to hold a second radio and a second input configured toconnect to an input of the second radio; a passive powerdivider/combiner coupled to the first input and the second input, thepassive power divider/combiner configured to passively combine RFsignals from the first and second input and output them to an antennaport and to divide RF signals from the antenna port between the firstand second inputs; and an antenna mount for holding a single antenna,wherein the antenna port is in or adjacent to the antenna mount.

In some variations the apparatuses may include the radio(s) and/or thesingle antenna. The antennas (e.g., the single antennas) into which theplurality of master radio devices feed may be any type of antenna. Forexample, as used herein, a single antenna may include a single reflector(e.g., parabolic dish) for both transmitting and receiving or it mayrefer to a compound antenna having a dedicated Tx reflector and adedicated Rx reflector, or it may include an array antenna that operatesas a single antenna (e.g., micro strip array antenna). The singleantenna may be a directional antennas or a non-directional (e.g., omni)antenna. The type of antenna is generally not relevant to combining ofthe radios on the single antenna. For example, the combining could occuras several multi-point access points combined on a single omni antenna(e.g., two or more combined) communicating with individual (client)subscribers. Multiple point-to-point masters radios on a single antenna(which could be an omnidirectional antenna) may link to individualpoint-to-point slaves radios on individual antennas in differentdirections around the single antenna (master radios).

Any of the apparatuses described herein may be integrated with either orboth the radio(s) and/or the antenna. For example, a multiplexerapparatus for combining a plurality of radios so that theysimultaneously send or receive from a single antenna may include: afirst external mount configured to hold a first radio, and a first inputconfigured to connect to an input of the first radio; a second externalmount configured to hold a second radio and a second input configured toconnect to an input of the second radio; a passive powerdivider/combiner coupled to the first input and the second input, thepassive power divider/combiner configured to passively combine RFsignals from the first and second input and output them to an antennaport and to divide RF signals from the antenna port between the firstand second inputs; and a single antenna coupled to the first and secondexternal mounts, wherein the antenna feed is coupled to the antennaport.

As mentioned, in any of these apparatuses the passive powerdivider/combiner may be a Wilkinson divider/combiner.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe claims that follow. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1A is a schematic illustrating a system as described hereincomprising one example of a multi-radio antenna apparatus having aplurality of n radios all connected (e.g., through one or moredividers/splitters coupled at the antenna feed) to the same antenna;each radio is also connected to a networking device (e.g., router) thatautomatically load-balances the radios.

FIGS. 1B and 1C show side and bottom views, respectively of one exampleof a multiplexer apparatus configured to combine a plurality of radiosso that they simultaneously send or receive from a single antenna.

FIG. 1D illustrates a system including a multiplex such as the one shownin FIGS. 1B and 1C and a router.

FIG. 2 schematically illustrates example of 3:1 (on left) and 2:1 (onright) multi-radio antenna apparatuses as described herein.

FIG. 3A is an example of a back of an antenna as described herein,including a radio mount for a single radio.

FIG. 3B shows an example of a back of an antenna having a housing/mountfor two radios as described herein.

FIGS. 4A-4D show one example of a multi-radio antenna apparatus that ishighly synchronized as described herein, from isometric, side, front andback views, respectively.

FIGS. 5A-5D illustrate another example of a multi-radio antennaapparatus similar to the variation shown in FIGS. 4A-4D above, includinga mount for a pair of radios (though additional radios may be used,including dynamically added/removed, without disruption or loss of data,as described herein.

FIG. 6 is an exploded view of the multi-radio antenna apparatus of FIGS.5A-5D.

FIG. 7 is an example of one variation of a power splitter/power combinerthat may be used with any of the apparatuses described herein. In thisvariation, the power divider (also referred to herein as a powersplitter, and power combiner) is a Wilkinson powerdivider/splitter/combiner and is coupled to the feed of the antennaemitter, as shown.

FIGS. 8A and 8B show example of an antenna emitter assembly including apower divider as described herein.

FIG. 9 is an exploded view of the antenna emitter assembly shown inFIGS. 8A and 8B.

FIG. 10A illustrates the sub-optimal transmission and receiving using anunsynchronized combined (multiplexed) system of two (master) radiossharing a single antenna, showing overloaded conditions that may resultbetween the two radios both attempting to transmit and receive from thesame antenna, when communicating with two remote (slave) radio devices.

FIG. 10B illustrates transmission and receiving using a synchronized(e.g., via GPS) multiplexed system of two (master) radios sharing asingle antenna. External synchronization by GPS in combination with thepassive combiner/splitter allows highly economical concurrenttransmission by different radios even at immediately adjacent frequencybands without needing the use of a guard band between them. FIG. 10Balso shows how different slave radios may be synchronized with themultiplexed master radios when the master radios are operating in ashared antenna mode.

FIG. 11 schematically illustrates one variation of a method of combininga plurality of radios so that they simultaneously send or receive from asingle antenna, as described herein.

DETAILED DESCRIPTION

Described herein are multi-radio antenna apparatuses and stations forwireless networks including multiple radios coupled to a singletransmit/receive antenna, in which the antenna (and/or the radios) ishighly synchronized. These multi-radio antenna systems may providehighly resilient links. Synchronization (e.g., GPS synchronization) mayallow these apparatuses to organically scale the transmission throughputwhile preventing data loss. The single transmit/receive antenna may havea single dish or a compound (e.g., a single pair of separatetransmitting and receiving dishes) and connections for two or moreradios. These apparatuses may be configured for frequency divisionmultiplexing with concurrent transmission from each of the radios out ofthe same antenna, with minimal or no isolation between radio units.

In general, the apparatuses described herein include a single antennaassembly that is couples to an operates with a plurality (e.g., 2 ormore, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more,9 or more, . . . n or more, or between 2 to n, between 3 to n, between 4to n, etc. where n is 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18, etc.). The antenna assembly typically includes a single combinedtransmitting/receiving antenna emitter/detector (transceiver or simply“emitter” for convenience), or a pair of transmitting antenna emitterand receiving antenna detector (see, e.g., US 2014/0218255).

The antenna assembly may also include an emitter (e.g., combinedemitter/absorber for transmitting and/or receiving RF energy). Theemitter may be mounted within a reflector (e.g., parabolic reflector).The emitter/absorber surface may include one or more feeds (e.g.,horizontal and vertical, or other polarization feeds) and each feed mayinclude one or more power splitters/power combiners, such as, e.g., aWilkinson power splitter/power combiner. The power splitter/powercombiners may be nested (e.g., multiple power splitter/power combinermay be connected together to multiply divide the signals between theplurality of radios associated with the apparatus. The powersplitter/power combiner may be 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:m,2:3, 2:4, 2:5, 2:6, 2:7, 2:8, 2:9, 2:10, 2:p, etc. For example, theapparatus may include a lumped element 2-2ay Wilkinson splitter/combinercoupled to the feed(s) of the antenna, through which the differentradios connect to the emitter. Wilkinson power splitter/power combinersmay be particularly useful, as they may be compact and do not typicallyrequire special electronics.

Although the use of power splitter/power combiners as described aboveand shown here may result in a loss in overall power of the transmittedsignal (e.g., this loss has been measured as about 3.5-4 dB), thetradeoff may be an increase in throughput. When the radios are highlysynchronized (e.g., using a high-accuracy GPS signal) and/or whenoperated with a networking device (e.g., router) that can dynamicallymonitor and balance the operation of the radios, the result is a highlyscalable increase in signal throughput (which may linearly scale as thenumber of radios increases) without loss or delay as radios areremoved/fail.

Any of the antenna assemblies described herein may include GPSsynchronization that is sufficient to synchronize within appropriatetiming (e.g., within less than 100 ms, 50 ms, 25 ms, 10 ms, 5 ms, 1 ms,0.5 ms, 0.1 ms, 0.05 ms, 0.01 ms, etc.) so that the radios receive andtransmit on the same, nearly-identical (within the timing parametersjust mentioned) schedule, without requiring any coordination between theradios. This transmitting/receiving schedule may be regularly‘refreshed’ by the accurate GPS signal, and each radio may be configuredto operate within a predetermined schedule. The use of the highlyaccurate GPS timer as described may allow the radios to function in acoordinated manner by the pre-set, shared schedule, without requiringthat the radios talk with each other or with other systems before theytransmit and/or receiver. Thus, the radios do not need to handshake orotherwise communicate back and forth with each other, which wouldtypically delay operation. The apparatuses (which may generally includedevices and systems) described herein typically use the GPS signals as areference clock and do not have to talk with each other, or even beaware of each other to function in a coordinated, and therefore moreefficient manner. Instead, the radios may send and/or receive dataframes based on the preset schedule and the GPS clock withoutcoordinating/communication between the radios. The use of the GPStiming, when the accuracy is sufficiently high, may allow an intelligentarchitecture such that dividing multiple radio signals between one ormore antennas may be successfully performed.

Any of the apparatuses described herein may use any appropriate signalmultiplexing technique. In particular, the apparatuses described hereinmay use frequency division multiplexing. Frequency division multiplexingmay allow a plurality of radios coupled to the same antenna apparatus totransmit at the same time and receive at the same time using theapparatus architecture described herein.

For example, the synchronized radios may be configured on a repeatingand/or resetting schedule that determines when transmission occurs, whenreceiving occurs. For example a GPS synchronizing signal may initiate acycle in which, e.g., every second a counter is re-set so thattransmission occurs every 200 ms; at the end of a predetermined period,the cycle is re-set by the GPS synchronization in all of the radios,therefore the radios get re-time synched at the next second.Alternatively, another architecture may include the use of filters; theuse of synchronizing GPS as described herein may prevent or reduce theneed for this level of signal filtering, which may be expensive andlossy.

In general, radios may be configured to each receive the synchronizingsignal (GPS signal) directly or from the antenna assembly that they areconnected to. For example, an antenna assembly may include connections(docks, attachments, etc.) for connecting to a plurality of radiodevices, and may also include the high-accuracy GPS synchronizingcircuitry described herein; alternatively or additionally, the radiosmay be configured to receive directly the GPS synchronizing/timingsignal.

In general, each radio may be operating within a different (e.g.,offset) frequency range within the bandwidth of the antenna assembly.For example, when three radios are used, the upper, middle and lowerfrequency ranges of the bandwidth of the antenna may be parsed betweenthe three radios. The antenna assembly may set the frequency range foreach radio.

The apparatuses described herein may allow on-the-fly addition/removalof radio devices. For example, the systems may include radios that areadded/removed or degrade during operation without interrupting thetransmission. Thus, these apparatuses may operate at full capacity evenas one or more radios are added/removed or degrading. This functionalitymay be enhanced by the use of a networking device such as a router, orother controller, that monitors the radio operation/throughput, anddynamically balances the transmission loads between the differentradios. Any of the apparatuses (e.g. multi-radio antenna systems)described herein may therefore be load-balanced multi-radio antennasystems and may include or be configured to operate with a controller(e.g., network device, router, etc.) that load balances between theradios.

Thus, any of these apparatuses may automatically load balance betweenthe radio devices coupled to the same antenna. The network device (andtherefore the system) may thus detect when a radio that is connected tothe antenna has degraded (e.g., reduced throughput, efficiency, and/orfailed, etc.) and re-balance between the remaining radios, e.g., byswitching which radios transmit the ‘load’ of data packets. Unlike othersystems that may require down-time while switching, the apparatusesdescribed herein may constantly evaluate the capacity of the radio(s)connected and may detect failure; when failure or performancedegradation (or improvement) is detected, the apparatus may handle it byadjusting the load. In general, the apparatuses (e.g., network devices,routers, etc.) described herein may detect the change in capacitybetween radios in terms of Mbit/sec balance based on the changes inrate.

For example, FIG. 1 is a schematic of one example of a system asdescribed herein. In this example the apparatus includes a single-dish(TX/RX) 105 antenna 103 that receives high-accuracy GPS data andcommunicates it to each of a plurality of radios that are connected 107,107′, 107″, etc. The radios are all connected to a networking device 109(e.g., a router) that can monitor and balance the data loads between thedifferent radio devices. In this example, the router may be part of theoverall apparatus (e.g., the antenna) or it may be located remotely(immediately nearby, e.g., short cable connection, or connected by longcabling). The networking apparatus may also include a fiber uplink sothat the apparatus can feed power (e.g., DC power) to the rest of thesystem (e.g., radios and/or antenna).

Load balancing may be done automatically, e.g., after an initialset-up/detection step, or it may be user adjusted/modified. Appendix A,attached hereto, including one example of an apparatus (configured as arouter) that may be used as described herein.

FIG. 2 schematically shows one variation of two systems (one with 3radios on the left, another with 2 radios, on the right). In eitherexample, the apparatus may include a 3:1 or 4:1 splitter or more (e.g.,5:1, 6:1, 7:1, 8:1, etc.); the additional radios may be absent; theapparatus (by itself or in combination with a separate networking device(e.g. router) may provide the load balancing. As discussed above, the“diplexers” shown (3:1, 2:1) in this example may besplitter/divider/combiners, such as Wilkinsonsplitter/divider/combiners.

In general, any of the apparatuses described herein may include multipleradios and may be adapted to hold or secure these radios onto the backof the apparatus, as shown in FIG. 3A (showing a back mount for a singleradio 305) and FIG. 3B (showing a back mount configured to hold tworadios 307, 307″. Additional radios may be connected (e.g., by cables)or to an auxiliary mount (not shown).

FIGS. 4A-4D illustrate one example of a multi-radio apparatus. In thisexample, a single reflector 401, includes an emitter (not visible)within the mouth of the antenna assembly 405 to which one or moresplitter/divider/combiners are attached. In general,splitter/divider/combiners may be chained in series and/or parallel toprovide additional splitting/combining of the signal; although this mayresult in power loss, the benefits in throughput may outweigh thedisadvantages. The back of the device (visible in FIGS. 4B and 4D) mayinclude mounts/connectors for connecting to a plurality of radios. Eachradio may, without communicating with each other at all, synchronouslytransmit from the same emitter and reflector (antenna dish), asdescribed above.

The variation shown in FIGS. 5A-5D is similar to that shown in FIGS.4A-4D, but includes a mount 501, similar to that shown in FIG. 3B. Anexploded view of this apparatus is shown in FIG. 6, showing thereflector 601, the mount and radio holder(s) 605, housing 603, a tube(waveguide) 607 and the emitter with coupled splitter/divider/combiner610. The networking device is not shown, but may be connected to eachradio (also not shown) within the radio apparatus. The apparatus may bemounted to a pole, wall, post, etc., either indoor or outdoor(preferably outdoor).

FIG. 7 shows one example of an emitter of a multi-radio synchronizedantenna apparatus as described above, including a pair ofsplitter/divider/combiners. In this example thesplitter/divider/combiner are Wilkinson-type splitter/divider/combiner701; each polarization feeding into the emitter is attached to asplitter/divider/combiner (e.g. a 2:1, 4:1, etc.splitter/divider/combiner, etc.). This structure, or one like it, may beincorporated into any of the apparatuses described herein. For example,FIGS. 8A and 8B show one example of a portion of the antenna apparatusof FIGS. 5A-5D. In this example the emitter 805 is fed by a pair offeeds 807, 809 which are connected directly to one or moresplitter/divider/combiners (e.g., multiple splitter/divider/combinersmay be connected to each other in series) (not shown). Eachsplitter/divider/combiners may be connected to each radio of theplurality of radios, as described above, and each radio may in turn beconnected to the networking device that may monitor and load-balance theradios.

The emitter portion (emitter/absorber) portion shown in FIGS. 8A and 8Bmay also be connected within the antenna apparatus to the RF signalchannel, such as an RF waveguide (see, e.g., FIGS. 4A-4C, 5A-5C, and 6)which, along with a reflector (e.g. parabolic reflector) may channel theRF energy to/from the apparatus.

FIG. 9 shows an exploded view of the emitter assembly shown in FIGS. 6Aand 6B, including the emitter/absorber 901 having two or more feeds (notvisible, e.g., for vertical and horizontal or other polarizations), asplitter/divider/combiners 903, and multiple connectors 905 forconnecting (in this example, 4 are shown) to the multiple radios thatmay be connected. The housing 907 may include multiple componentsincluding brackets 911, fasteners 913, and mounts 915, 917.

EXAMPLES

In some embodiments of the methods and apparatuses described herein, theapparatus is a scalable MIMO Multiplexer having a very reduced footprintbecause it can efficiently combine multiple radios with a single antenna(e.g., in some variations a single reflector). FIGS. 1B-1D illustrateexamples of such a multiplexing apparatus, which may be referred to asan “N×N” MIMO multiplexer. This apparatus may have multi-gigabitthroughput, and also allows redundancy between the included radios,without the need for additional antennas. Each of the radios maytransmit synchronously and receive synchronously. Because they aresynchronized and their RF signals passively mixed by the multiplexer,they may simultaneously communicate from the same antenna with verylittle Rx degradation/interference (e.g., cross-talk, etc.); each radiomay transmit at a different frequency band, and these bands may beimmediately adjacent, without the need for a guard band between nearbyfrequency bands.

FIG. 1B shows an example of a multiplexer having four attached radiodevices 107, 107′, shown mounted, e.g., on a tower or post. Themultiplexer is integrated with a single antenna, in this variationhaving a parabolic dish 105 for Tx/Rx. FIG. 1C shows a bottom view ofthis apparatus, showing the four radios in which two of the radios are“offline” while the remaining two radios remain dynamically connected tothe multiplexer, illustrating the redundancy. Even when some of theradios are offline, as long as one of the radios is online, the linkremains active.

The methods and apparatuses described herein typically synchronize each(master) radio extremely accurately through their GPS clock receivers.RF timeslots are framed and transmitted to allow multiple radios to syncwithout being in communications with each other and without requiringany direct electrical connection (e.g., wiring) between them. Thesemethods and apparatuses embodying them are sufficiently accurate so thatthere is little or no interference between the radios which all transmitand receive at nearly exactly the same time (within tens ofnanoseconds). Thus each local (master) radio will not transmit whenanother local (master) radio is receiving or vice versa.

In any of the variations described herein, each of the radios may use acommon GPS timing reference. All of the (master) radios in themultiplexer may independently receive the GPS timing reference. Anydownstream (slave) radios may also reference the same external GPStiming signal; in some variations it is not necessary that the slavedevices reference the external GPS timing signal. The slave devices mayinstead synchronize their duty cycle off of the preamble (masterpreamble symbols) transmitted by the radio(s) as part of theirtransmission frame (during the Tx portion), prior to transmission of theTx symbols.

As described above, in general, the ports (output/input) for each of theradio devices connect to the same antenna device through a passivecombiner/splitter that can combine the input/output for all of the radioapparatuses (for each polarization, for example) into a singleinput/output for the antenna. In some variations a Wilkinson splitter(also referred to as a Wilkinson combiner, Wilkinson divider, etc.) is awide-band multi-port and passive construct which can take a single inputand splits it into two or more outputs, keeping a level of isolationbetween the input and outputs and the two outputs themselves. As apassive device, it works in the opposite direction, as a combiner.

In the methods and apparatuses described herein, when operating in ashared antenna mode, the transmitting/receiving is done in the timedomain (instead of the frequency domain), and the radios may includeadjacent channel rejection characteristics, and be used with a very lownoise power amplifier, allowing two channels directly next to eachother.

In the methods and apparatuses described herein, the bands for eachradio may have any appropriate channel width. For example, two or more50 MHz links (each corresponding to a single master radio) may bedelivered from the same dish (assuming the spectrum is available), whichwould provide 800 Mb aggregate. As mentioned, the channels don't have tobe directly adjacent although they may be; the operating channels foreach radio can be anywhere in the band. The band of each radio may be ofany appropriate size, and may be different from each other. Note thateach radio may provide multiple polarizations (e.g., horizontal,vertical, etc.). These different polarizations may also be passivelycombined. In some variations all of RF signals of a particularpolarization for all of the radios may be passively combined and fed tothe same antenna. In some variations, different passivecombiners/splitters may be used for each polarization. In somevariations the same passive combiner/splitter may be used.

Although the disclosure herein describes the advantages and use ofpassive combiner/splitters such as the Wilkinson splitter, anyappropriate passive combiner/splitter may be used. A Wilkinson combinertypically allows combining with little frequency selectivity but thereare many other broadband and combiners that may be used to sum the radiosignals on one single antenna. Further, these methods and apparatusesare not limited to passive combiners; the same principles may apply toactive combiner/splitter subsystems, and therefore such activecombiner/splitters may alternatively be used in any of these methods anddevices. In addition, some of the concepts (e.g., GPS synchronization)may also be applied even without combiner/splitters and a singleantenna. For example, multiple radios each connected to separateantennas may be synchronized, particularly where the antennas areadjacent/near but separated by a physical isolation/boundary or barrier(e.g., “choke boundary”).

Note that in some variations the apparatuses and methods may allowoperating in other modes which may not include the benefits describedherein for the shared antenna mode, but may allow operation of the radiodevices even in the absence of external (e.g., GPS) synchronizationbetween these radio devices. Other modes may also allow frequency-domainoperation. In some variations the apparatuses described herein may beconfigured to switch between modes, e.g., between the synchronized“shared antenna mode” and other modes that may not be externallysynchronized, including frequency-domain operational modes. Switchingmay be done manually or automatically. Automatic switching may beperformed based on the presence/absence of the GPS timing signal (or thestrength of the signal), based on signal quality considerations, and/orbased on spectral information (e.g., available bandwidths).

As mentioned, any of these apparatuses may also be used as part of aMIMO configuration. For example, with two radios connected andmultiplexed to a single antenna as described herein 4×4 MIMO may beachieved (with 2× faster throughput); with four radios, 8×8 MIMO may beused (with 4× faster throughput).

FIG. 1D shows an example of a multiplexing apparatus 101 coupled with arouter 155 and two or more radios 107, 107′, so that each radio deviceis connected to the same router, which may allow load balancing betweenthe different radios. In the variation shown in FIGS. 1B-1D, themultiplexing apparatus 101 is coupled with the antenna 105; in somevariations the antenna is not integrated with the multiplexing apparatusbut is separate. In some variations the antenna is integrated with themultiplexing apparatus. Similarly, the radios may be separate (asillustrated in FIGS. 1B-1D) or integrated with the multiplexingapparatus.

In general, in variations in which the radios are not integrated intothe multiplexing apparatus, the multiplexing apparatus may include aplurality of radio mounts for securely connecting each radio to theapparatus. For example, the housing may include bays or slots into whicheach radio device may be secured. One or more ports for each radiodevice (not visible in FIGS. 1B-1D) may be near or within each bay orport, to allow connection between each radio device (e.g., the verticaland horizontal input/outputs of each radio) and the apparatus. The portsmay be formed in the housing, including in an external housing, allowingquick and easy access to each radio device. The connections may beprotected from the elements by a cover, housing or the like.

FIG. 11 describes one method of combining a plurality of radios so thatthey simultaneously send or receive from a single antenna (“sharedantenna mode”), as described herein. In general, the method may include(optionally) connecting each of the radio devices (RF radios) to amultiplexer apparatus so that the inputs/outputs of the radio devicesare connected to the multiplexer apparatus. These inputs/outputs of eachof the plurality of radios may then be passively combined into a singleinput/output that is coupled to the single antenna 1101. Alternatively,separate input/outputs for separate polarizations may be combined forall of the radios and connected (separately) to the antenna.

Each of the radios may generally include a GPS receiver and controlcircuitry (hardware/firmware) for receiving and processing a GPS timingsignal. During operation of the multiplexer in the shared antenna mode,all of the connected (master) radios may be synchronizing using a GPStiming pulse signal, so that each of the plurality of radios isoperating on a same duty cycle 1103. Synchronization may be periodicallyand/or regularly (e.g., every 1 second, 2 seconds, etc.) repeated. Eachof the radios may then transmit synchronously and receive synchronouslyaccording to the synchronized duty cycle. Slave devices receiving andtransmitting to the multiplexed ratios may synchronize to the same dutycycle, as will be described in greater detail below.

In general, operation of this method may be regulated and/or controlledby control logic in the multiplexer (e.g., using circuitry, e.g.,hardware, and/or firmware and/or software), the radios, and/or a routerconnected to the multiplexer. For example, the multiplexer maycommunicate with each radio to indicate that shared antenna mode isoperating, and therefore establish the duty cycle that each of theradios will be operating in, as well as indicating that the radio shouldsynchronize via the external GPS signal. Similarly the multiplexer mayreceive information from one or more of the radios to determine if theapparatus should enter/remain in shared antenna mode (e.g., based on thepresence/absence of a GPS signal, signal degradation, etc.)

In the shared antenna mode, each radio may simultaneously transmit 1105,and may also transmit a synchronized master timing preamble that may beused to synchronize the receiving (slave) radios in the link pair(s). Asmentioned, each of the plurality of radios may operate in differentfrequency channels, which may be directly adjacent and without using aguard band between adjacent Tx frequency bands (e.g., “end-to-end”).Each radio may also simultaneously receive (Rx) RF signals during theappropriate and synchronized portion of the duty cycle using the sameantenna 1107. As mentioned, any of these methods may also includesynchronizing the slave (e.g., the duty cycle for Tx/Rx) in the link ofa first remote slave radio using the master timing preamble.

FIGS. 10A and 10B illustrate transmission links between multiplexedmaster radios and two linked slave radios. FIG. 10A shows an example ofan asynchronous, frameless protocol. In this example, both mater (accesspoint) radios are asynchronous in timing, and combining these radioswould result in de-sensed (overloaded) receiving during the asynchronoustransmission from slave devices, as illustrated by the underlinedregions. Similarly, the slave devices would also suffer from desensed Rxtransmission (overload).

FIG. 10B schematically illustrates Tx/Rx during a shared antenna mode,having synchronous framed protocol. On the left, the two master radiosare synchronized and passively multiplexed as described above. Bothradios transmit or send at nearly exactly the same time, avoidingreceiver degradation. The right side of FIG. 10B shows the Tx/Rx framesfor each of two downlink radio devices (“slaves”). The first onesynchronizes fully with the multiplexed master (as shown) by correctlyidentifying the master preamble indicating the start of the Tx framefrom the master and setting the duty cycle for the slave radio. Thus,the first slave is aligned. The second slave (“Slave device 2”) at thesecond frequency (“Freq B”) does not immediately synchronize to themaster preamble 1007, but instead mistakenly synchronized to a local“slave preamble” (e.g., from the other slave device, etc.). This resultsin an invalid synchronization and overloading of the second slave radio.As shown 1009, the second slave radio may then slide the receiver frameto look for the correct master preamble. When it finds the correctmaster preamble 1011, the second slave radio may then properlysynchronize with the remote master preamble, and being returntransmissions. Thus, the slave radios may look for and identify thecorrect master beacon (master preamble symbols) to synchronize with theradio(s) in the multiplexed device.

When a feature or element is herein referred to as being “on” anotherfeature or element, it can be directly on the other feature or elementor intervening features and/or elements may also be present. Incontrast, when a feature or element is referred to as being “directlyon” another feature or element, there are no intervening features orelements present. It will also be understood that, when a feature orelement is referred to as being “connected”, “attached” or “coupled” toanother feature or element, it can be directly connected, attached orcoupled to the other feature or element or intervening features orelements may be present. In contrast, when a feature or element isreferred to as being “directly connected”, “directly attached” or“directly coupled” to another feature or element, there are nointervening features or elements present. Although described or shownwith respect to one embodiment, the features and elements so describedor shown can apply to other embodiments. It will also be appreciated bythose of skill in the art that references to a structure or feature thatis disposed “adjacent” another feature may have portions that overlap orunderlie the adjacent feature.

Terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention.For example, as used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, steps, operations, elements, components, and/orgroups thereof. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items and may beabbreviated as “/”.

Spatially relative terms, such as “under”, “below”, “lower”, “over”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if a device in thefigures is inverted, elements described as “under” or “beneath” otherelements or features would then be oriented “over” the other elements orfeatures. Thus, the exemplary term “under” can encompass both anorientation of over and under. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly. Similarly, the terms“upwardly”, “downwardly”, “vertical”, “horizontal” and the like are usedherein for the purpose of explanation only unless specifically indicatedotherwise.

Although the terms “first” and “second” may be used herein to describevarious features/elements (including steps), these features/elementsshould not be limited by these terms, unless the context indicatesotherwise. These terms may be used to distinguish one feature/elementfrom another feature/element. Thus, a first feature/element discussedbelow could be termed a second feature/element, and similarly, a secondfeature/element discussed below could be termed a first feature/elementwithout departing from the teachings of the present invention.

Throughout this specification and the claims which follow, unless thecontext requires otherwise, the word “comprise”, and variations such as“comprises” and “comprising” means various components can be co-jointlyemployed in the methods and articles (e.g., compositions and apparatusesincluding device and methods). For example, the term “comprising” willbe understood to imply the inclusion of any stated elements or steps butnot the exclusion of any other elements or steps.

As used herein in the specification and claims, including as used in theexamples and unless otherwise expressly specified, all numbers may beread as if prefaced by the word “about” or “approximately,” even if theterm does not expressly appear. The phrase “about” or “approximately”may be used when describing magnitude and/or position to indicate thatthe value and/or position described is within a reasonable expectedrange of values and/or positions. For example, a numeric value may havea value that is +/−0.1% of the stated value (or range of values), +/−1%of the stated value (or range of values), +/−2% of the stated value (orrange of values), +/−5% of the stated value (or range of values), +/−10%of the stated value (or range of values), etc. Any numerical valuesgiven herein should also be understood to include about or approximatelythat value, unless the context indicates otherwise. For example, if thevalue “10” is disclosed, then “about 10” is also disclosed. Anynumerical range recited herein is intended to include all sub-rangessubsumed therein. It is also understood that when a value is disclosedthat “less than or equal to” the value, “greater than or equal to thevalue” and possible ranges between values are also disclosed, asappropriately understood by the skilled artisan. For example, if thevalue “X” is disclosed the “less than or equal to X” as well as “greaterthan or equal to X” (e.g., where X is a numerical value) is alsodisclosed. It is also understood that the throughout the application,data is provided in a number of different formats, and that this data,represents endpoints and starting points, and ranges for any combinationof the data points. For example, if a particular data point “10” and aparticular data point “15” are disclosed, it is understood that greaterthan, greater than or equal to, less than, less than or equal to, andequal to 10 and 15 are considered disclosed as well as between 10 and15. It is also understood that each unit between two particular unitsare also disclosed. For example, if 10 and 15 are disclosed, then 11,12, 13, and 14 are also disclosed.

Although various illustrative embodiments are described above, any of anumber of changes may be made to various embodiments without departingfrom the scope of the invention as described by the claims. For example,the order in which various described method steps are performed mayoften be changed in alternative embodiments, and in other alternativeembodiments one or more method steps may be skipped altogether. Optionalfeatures of various device and system embodiments may be included insome embodiments and not in others. Therefore, the foregoing descriptionis provided primarily for exemplary purposes and should not beinterpreted to limit the scope of the invention as it is set forth inthe claims.

The examples and illustrations included herein show, by way ofillustration and not of limitation, specific embodiments in which thesubject matter may be practiced. As mentioned, other embodiments may beutilized and derived there from, such that structural and logicalsubstitutions and changes may be made without departing from the scopeof this disclosure. Such embodiments of the inventive subject matter maybe referred to herein individually or collectively by the term“invention” merely for convenience and without intending to voluntarilylimit the scope of this application to any single invention or inventiveconcept, if more than one is, in fact, disclosed. Thus, althoughspecific embodiments have been illustrated and described herein, anyarrangement calculated to achieve the same purpose may be substitutedfor the specific embodiments shown. This disclosure is intended to coverany and all adaptations or variations of various embodiments.Combinations of the above embodiments, and other embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the above description.

What is claimed is:
 1. An apparatus for transmitting radio signalscomprising: a first radio and a second radio; at least one sharedantenna from which the first and second radios both transmit andreceive; at least one global positioning system (GPS) receiver; and amultiplexer configured to connect to the first and second radios, themultiplexer comprising a controller configured to switch operation ofthe apparatus from a first, externally synchronized, mode, in which thefirst and second radios are synchronized based on a GPS timing signal,and a second mode that is not externally synchronized, wherein the firstmode comprises a time domain mode, in which the first and second radiosoperate a time domain, and wherein the second mode comprises a frequencydomain operational mode, in which the first and second radios operate afrequency domain.
 2. An apparatus for transmitting radio signalscomprising: a first radio and a second radio; at least one sharedantenna from which the first and second radios both transmit andreceive; at least one global positioning system (GPS) receiver; and amultiplexer configured to connect to the first and second radios, themultiplexer comprising a controller configured to switch operation ofthe apparatus from a first, externally synchronized, mode, in which thefirst and second radios are synchronized based on a GPS timing signal,and a second mode that is not externally synchronized, wherein the firstand second radios operate on a same duty cycle in the first mode.
 3. Theapparatus of claim 1, wherein the first and second radios areperiodically synchronized in the first mode.
 4. The apparatus of claim1, wherein the multiplexer comprises a passive power divider/combinerconfigured to couple to the first and second radios and to passivelycombine radio frequency (RF) signals from the first and second radios inthe first mode.
 5. The apparatus of claim 4, wherein the passive powerdivider/combiner is configured to output the combined RF signals to anantenna and to divide RF signals from the antenna between the first andsecond radios.
 6. The apparatus of claim 1, wherein the multiplexer isconfigured to switch between the first and second modes automaticallybased on a presence or absence of the GPS timing signal.
 7. Theapparatus of claim 1, wherein the multiplexer is configured to switchbetween the first and second modes based on a strength of the GPS timingsignal.
 8. An apparatus for transmitting radio signals comprising: afirst radio and a second radio; at least one shared antenna from whichthe first and second radios both transmit and receive; at least oneglobal positioning system (GPS) receiver; and a multiplexer configuredto connect to the first and second radios, the multiplexer comprising acontroller configured to switch operation of the apparatus from a first,externally synchronized, mode, in which the first and second radios aresynchronized based on a GPS timing signal, and a second mode that is notexternally synchronized, wherein the multiplexer is configured to switchbetween the first and second modes based on available bandwidths.
 9. Theapparatus of claim 1, wherein each of the first and second radios isconfigured to independently receive the GPS timing signal.
 10. Anapparatus for transmitting radio signals comprising: a first radio and asecond radio; at least one shared antenna from which the first andsecond radios both transmit and receive; at least one global positioningsystem (GPS) receiver; and a multiplexer configured to connect to thefirst and second radios, the multiplexer comprising a controllerconfigured to switch operation of the apparatus from a first, externallysynchronized, mode, in which the first and second radios aresynchronized based on a GPS timing signal, and a second mode that is notexternally synchronized, wherein when the first and second radiostransmit synchronously and receive synchronously according to a sameduty cycle.
 11. An apparatus for transmitting radio signals comprising:a first radio and a second radio; at least one shared antenna from whichthe first and second radios both transmit and receive; at least oneglobal positioning system (GPS) receiver; and a multiplexer configuredto connect to the first and second radios, the multiplexer comprising acontroller configured to switch operation of the apparatus from a first,externally synchronized, mode, in which the first and second radios aresynchronized based on a GPS timing signal, and a second mode that is notexternally synchronized, wherein the first and second radios areconfigured to operate in adjacent frequency channels without a guardband between the adjacent frequency channels in the first mode.
 12. Anapparatus for transmitting radio signals comprising: a first portconfigured to receive a first radio; a second port configured to receivea second radio; at least one shared antenna from which the first andsecond radios both transmit and receive; a multiplexer configured toconnect to the first and second radios, the multiplexer comprising acontroller configured to switch operation of the apparatus from a first,externally synchronized, mode, in which the first and second radios aresynchronized based on a GPS timing signal, and a second mode that is notexternally synchronized wherein the first mode comprises a time domainmode, in which the first and second radios operate a time domain, andwherein the second mode comprises a frequency domain operational mode,in which the first and second radios operate a frequency domain; and apassive power divider/combiner configured to couple to the first andsecond radios and to passively combine radio frequency (RF) signals fromthe first and second radios in the first mode.
 13. A method oftransmitting radio signals from a first radio and a second radio thatshare at least one antenna, the method comprising: detecting a globalpositioning system (GPS) timing signal; operating the first and secondradios in a first, externally synchronized, mode in the presence of aGPS timing signal wherein the first and second radios are synchronizedbased on the GPS timing signal; operating the first and second radios ina second mode that is not externally synchronized in the absence of aGPS timing signal; and transmitting radio frequency (RF) signals fromthe first and second radios from at least one antenna, wherein the RFsignals from the first and second radios are simultaneously transmittedin the first mode, wherein the first and second radios operate in a timedomain in the first mode, and in a frequency domain in the second mode.14. A method of transmitting radio signals from a first radio and asecond radio that share at least one antenna, the method comprising:detecting a global positioning system (GPS) timing signal; operating thefirst and second radios in a first, externally synchronized, mode in thepresence of a GPS timing signal wherein the first and second radios aresynchronized based on the GPS timing signal; operating the first andsecond radios in a second mode that is not externally synchronized inthe absence of a GPS timing signal; and transmitting radio frequency(RF) signals from the first and second radios from the at least oneantenna, wherein the RF signals from the first and second radios aresimultaneously transmitted in the first mode, wherein the first andsecond radios operate on a same duty cycle in the first mode.
 15. Themethod of claim 13, further comprising passively combining the RFsignals from the first and second radios in the first mode.
 16. Themethod of claim 13, further comprising automatically switching betweenthe first and second modes based on a presence or a strength of the GPStiming signal.
 17. The method of claim 13, further comprising repeatedlysynchronizing the first and second radios in the first mode.
 18. Amethod of transmitting radio signals from a first radio and a secondradio that share at least one antenna, the method comprising: detectinga global positioning system (GPS) timing signal; operating the first andsecond radios in a first, externally synchronized, mode in the presenceof a GPS timing signal wherein the first and second radios aresynchronized based on the GPS timing signal; operating the first andsecond radios in a second mode that is not externally synchronized inthe absence of a GPS timing signal; and transmitting radio frequency(RF) signals from the first and second radios from the at least oneantenna, wherein the RF signals from the first and second radios aresimultaneously transmitted in the first mode, further comprisingoperating the first and second radios in adjacent frequency channelswithout a guard band between the adjacent frequency channels in thefirst mode.